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SPECIFICATION FOR THE REINSTATEMENT OF OPENINGS IN ROADS
S6 Flexible and Composite Roads
S6.1 Reinstatement Methods
S6.1.1 General
1) The Undertaker shall carry out the reinstatement in accordance with one of the following methods and should endeavour to achieve the greatest degree of immediate permanent reinstatement.
2) Permitted materials and layer thicknesses are specified in Appendices A1 to A4, A9, A10 and A11.
3) Where the Authority knows of any site with high sulphate levels it should advise Undertakers in advance of the works so that appropriate measures may be taken.
S6.1.2 Method A- All Permanent Reinstatement
The excavation shall be reinstated to a permanent standard at the first visit.
S6.1.3 Method B - Permanent Binder Course Reinstatement
1) The backfill, sub-base, base (roadbase) and binder course shall be reinstated to a permanent standard at the first visit.
2) The permanent binder course material, or an alternative interim material, shall be extended to the surface as the interim surface course, with or without a thin separating material layer of sand at the position of the binder course/surface course interface. An alternative interim material may be deferred set material.
3) On the second visit, all interim surfacing materials shall be removed, to the top of the binder course, typically by cold planing, and a permanent surface course shall be laid.
4) Where a sand separation layer is present, prior to the reinstatement of the permanent surface course the sand shall be removed, the surface brushed clean and a tack coat applied.
S6.1.4 Method C - Permanent Base (Roadbase) Reinstatement
1) The backfill, sub-base and base (roadbase) shall be reinstated to a permanent standard at the first visit.
2) The interim surface course and part, or all, of the interim binder course, may be deferred set material. Part or all of the interim binder course may be an unbound granular material.
3) On the second visit, all interim surfacing materials shall be removed, to the top of the base (roadbase), and a permanent binder course and surface course shall be laid.
S6.1.5 Method D - Permanent Sub-base Reinstatement
1) The backfill and sub-base shall be reinstated to a permanent standard at the first visit
2) The interim base (roadbase) shall be granular and the interim surfacing shall be in accordance with the relevant requirements of Section S6.1.4.
3) On the second visit, all interim materials shall be removed, to the top of the sub-base, and a permanent base (roadbase), binder course and surface course laid.
S6.2 Sub-base Reinstatement
S6.2.1 General
Where the Authority knows of areas with drainage problems it should advise Undertakers in advance. Care must be taken to ensure that natural drainage is not adversely affected. If site conditions indicate to the Undertaker that the use of some sub-base materials may be detrimental to drainage, advice on the selection of suitable materials should be sought from the Authority.
Permitted options are shown in Appendix A1, subject to the following exceptions:
a) Sub-base Equivalence: The thickness of granular sub-bases may be reduced, provided that the thickness of the bituminous binder course is increased proportionately, in accordance with S6.3 4.
b) Small Reinstatements: A CBM3 sub-base of 150 mm thickness may be used in small excavations and narrow trenches regardless of whether the existing sub-base is cement bound. Where this option is utilised, the base (roadbase) material shall also be a bound material.
c) Alternative Reinstatement Materials: Alternative Reinstatement Materials (ARMs) may be laid at sub-base level, in accordance with Appendix A9, regardless of whether the existing sub-base is a bound material.
S6.3 Base (Roadbase) Reinstatement
S6.3.1 General
Permitted options are shown in Appendix A4, subject to the following exceptions:
S6.3.2 CBM3 in Flexible and Composite Roads
1) In Types 0 & 1 roads, where a CBM3 base (roadbase) is used, the reinstatement may either be surfaced on the same day or the CBM3 shall be allowed 7 days to cure before surfacing is undertaken. In either case, the CBM3 shall be allowed 7 days to cure before the road is opened to traffic.
2) In Types 2,3 & 4 roads, where the reinstatement is surfaced on the same day that the CBM3 base (roadbase) is placed, the road may be opened to traffic on the following day. Where the CBM3 base (roadbase) is not surfaced on the same day, the reinstatement shall be allowed 3 days to cure before surfacing is undertaken.
3) All composite roads constructed with a base (roadbase) of CBM3 lean-mix concrete or equivalent shall be reinstated with a CBM3 base (roadbase).
4) In composite roads, the reinstated CBM3 base (roadbase) shall be laid flush with the existing cement-bound base (roadbase).
5) Continuously reinforced concrete bases (roadbases) are not covered by this clause. Special conditions will apply to such reinstatement work and must be agreed with the Authority.
S6.3.3 Base (Roadbase) Equivalence
In Type 3 and 4 flexible roads, the thickness of granular bases (roadbases) may be reduced provided that the thickness of the bituminous binder course is increased proportionately, in accordance with the following requirements:
1) Each 10 mm increase in bituminous binder course thickness is equivalent to a 35 mm decrease in thickness of Type 1 Granular Sub-Base at base (roadbase) and/or sub-base levels.
2) This equivalence rule may be applied to include the total replacement of all granular materials at both sub-base and base (roadbase) levels, subject to the following restrictions:
a) Binder course and surface course thicknesses in Type 3 and 4 roads are minimum values and shall not be reduced by application of the 10:35 equivalence of bituminous/granular materials.
and b) Where part of a granular base (roadbase) and/or sub-base is to be replaced by additional binder course material, the remaining total thickness of granular material at base (roadbase) and/or sub-base level shall not be less than 150 mm.
S6.3.4 Modular Materials Within The Excavation
1) Where cobbles or setts are encountered during excavation, they may be recovered and reused for reinstatement of the relevant layer. Alternatively, at the discretion of the Undertaker, the layer may be reinstated using CBM3 laid to a thickness of 100 mm, or to match the original thickness, whichever is greater.
2) Layers of modules, cobbles/setts, stones, rocks, or other large aggregate particles laid upright, in an interlocking fashion, often termed `penning', will exhibit a greater stiffness than an equivalent layer of cobbles/setts laid horizontally. Where such upright interlocking modules are encountered, the layer shall be reinstated using CBM3 laid to a thickness of 100 mm, or to match the original thickness, whichever is greater.
3) Where surplus modules, cobbles or setts are removed from site, they shall remain the property of the Authority. The Undertaker shall notify the Authority and retain them for 10 days following such notification. Thereafter, the Undertaker shall be free to dispose of all remaining modules, cobbles and setts.
4) The Authority shall be informed of any material, cobbles or setts encountered which may be of historical or archaeological interest and shall be afforded the opportunity to inspect the material prior to it being covered.
5) Where CBM3 is used at base (roadbase) level, it shall be used in accordance with S6.3.2.
S6.3.5 Alternative Reinstatement Materials
Alternative Reinstatement Materials (ARMs) may be laid at base (roadbase) level, in accordance with Appendix A9, regardless of whether the existing base (roadbase) is a bound material.
S6.4 Surface Reinstatement
Permitted options are shown in Appendices A2 to A4 inclusive, subject to the following exceptions:
S6.4.1 Hot Rolled Asphalt (HRA) Surface
1) Type 0, 1 & 2 roads, where the existing surface course is HRA, shall be reinstated with HRA surface course, regardless of whether the running surface has a surface dressing or other surface treatment.
2) Type 3 & 4 roads, where the existing surface course is HRA which does not have a surface dressing or other surface treatment, shall be reinstated with HRA surface course.
S6.4.2 Stone Mastic Asphalt (SMA) and Thin Surface Course Systems
1) Where the existing surface course material is SMA or a thin surface course system the road shall be reinstated with SMA surface course, subject to the following requirements:
a) Existing SMA surface courses of nominal aggregate size greater than 10 mm shall be reinstated using 14 mm SMA, laid to a standard thickness of 40 mm.
b) Existing SMA surface courses of 10 mm nominal aggregate size or less shall be reinstated using 10 mm SMA, laid to a standard thickness of 30 mm.
c) The standard combined thickness of binder course and SMA surface course shall be 100 mm.
2) Edge and base preparation for permanent SMA reinstatements shall be as follows:
a) All edges shall be saw cut or trimmed by saw, to a depth of 40 mm or the thickness of the surface course, prior to permanent reinstatement.
b) A K1-40 tack coat shall be applied in accordance with S6.5.1.
c) An edge sealant shall be applied in accordance with S6.5.2.2.
3) Where the existing surface is a thin surface course material and the Authority does not want the reinstatement to be completed using SMA, the Authority shall contact the Undertaker in accordance with Section S6.4.5.5.
S6.4.3 Surface Course Material to BS 4987
Surface course material to BS 4987 shall be 10 mm CGSC, laid 40 mm thick subject to the following exceptions:
a) Types 0, 1 & 2 HRA surfaces (Section S6.4.1 1))
b) Non-overlaid Types 3 & 4 roads (Section S6.4.1 2))
c) SMA and thin surface courses surfaces (Section S6.4.2)
d) Other bituminous materials (Section S6.4.5)
S6.4.4 Binder Course Material to BS 4987
Where a dense binder course material to BS 4987 is to be used as the running surface for a period in excess of 6 months, the target binder content shall be increased by 0.5% above the BS 4987 target value.
S6.4.5 Other Bituminous Materials
Where it is necessary to use bituminous materials not included in Appendix A2, they shall be used in accordance with the following:
S6.4.5.1 General Requirements
1) Where existing road surfaces have been treated or constructed with high friction surfacings, porous asphalt or coloured surfacings and local custom and practice has been to complete all previous resurfacing with like materials, their permanent reinstatement shall be carried out in accordance with the following requirements:
a) High friction surfacings shall be permanently reinstated with like materials, or an agreed alternative material, in accordance with Section S6.4.5.2.
b) Porous asphalt surface courses shall be permanently reinstated with porous asphalt, or an agreed alternative material, in accordance with Section S6.4.5.3.
c) Coloured surfacings shall be permanently reinstated with like materials, or an agreed alternative material, in accordance with Section S6.4.5.4.
2) When requested by the Undertaker, the Authority shall identify an appropriate source of suitable like or alternative materials, wherever possible. Where the Authority is unable to identify an appropriate source of suitable material, the Undertaker shall provide a suitable material on the basis of best reasonable endeavours.
3) Where existing road surfaces have been treated or constructed with high friction surfacings, porous asphalt or coloured surfacings and local custom and practice has not been to complete all previous resurfacing with like materials, the Undertaker shall consult with the Authority to determine appropriate reinstatement requirements.
4) Where other specialist surfacing materials not included in Appendix A2 or Section S6.4.5.1 1) above have been used, they may generally be permanently reinstated in accordance with Section S6.4.5.5.
S6.4.5.2 High Friction Surfacings
1) High friction surfacings shall be permanently reinstated with a like material, applied at the earliest opportunity. The surface shall be permanently reinstated within 15 working days following the date of completion of the reinstatement, unless the prevailing weather conditions or other site circumstances mitigate against the successful application of the high friction surfacing. Where this occurs, the permanent reinstatement shall be deferred, until such time as the unfavourable weather conditions or other site circumstances abate.
2) Prior to the application of the permanent, or any interim, friction surfacing, warning signs shall be displayed indicating a potential slippery road surface.
S6.4.5.3 Porous Asphalt
1) Existing porous asphalt surface courses shall be permanently reinstated with a like material, with no permitted alternative materials, subject to the following exceptions:
a) Small reinstatements of less than 2.5 m overall length, which do not adversely affect the overall drainage characteristics of the site, may be reinstated using SMA.
b) Multiple small reinstatements using SMA shall not be closer than 3 m of each other in the principal direction of fall or surface drainage flow.
2) Porous asphalt surface courses shall be reinstated to nominally match the thickness of the existing layer.
3) The binder course of porous asphalt reinstatements shall be an asphalt material
4) Edge and base preparation for all permanent reinstatements in porous asphalt surfaces shall be as follows:
a) All edges shall be saw cut, or trimmed by saw, to a minimum depth of 50 mm (or the thickness of the surface course, if greater), prior to permanent reinstatement.
b) For permanent reinstatements using porous asphalt, all edges shall be cleared of all contamination and treated with a light application of tack coat, not edge sealant. A K1-40 tack coat shall be applied at a minimum rate of 0.5 to 0.7 l/m 2, in accordance with S6.5.1.
c) For permanent reinstatements using SMA, all edges shall be treated with edge sealant, preferably a non-rubberised sealant applied by spray. A K1-40 tack coat shall be applied to the base of the reinstatement in accordance with S6.5.1.
S6.4.5.4 Coloured Surfacings
Coloured surfacings used to highlight road features such as speed warnings, bus or cycle lanes, 'gateways' etc. shall be permanently reinstated using like materials of equivalent type and similar colour, subject to the following requirements:
a) Where the coloured surfacing is overlaid onto a road surface, a coloured overlay shall be applied to the same thickness.
b) Where the coloured surfacing is laid full depth, a coloured material shall be laid to the same thickness, wherever possible and practical. Where it is not possible or practical, the coloured surfacing material shall be reinstated by agreement.
S6.4.5.5 Other Specialist Surfacing Materials
1) Specialist surfacings not included in Appendix A2 or Section S6.4.5.1 1) shall generally be reinstated with SMA.
2) Where the overall area is sufficiently large to facilitate machine laying and the local custom and practice has been to complete all previous resurfacing with like materials and the Authority wishes to request the use of like materials, the Authority shall:
a) Notify the Undertaker accordingly at the planning or notice stage, or in the case of immediate works, before the permanent reinstatement.
b) Identify an appropriate source of suitable like or equivalent materials.
3) All other surfacing materials not covered above, including grouted bituminous materials, traffic calming materials, surface treatments etc., shall be permanently reinstated by agreement.
S6.4.6 Surface Treatments
1) In Types 0, 1 & 2 roads, where an existing surface dressing or other surface treatment is readily apparent, the Undertaker shall apply an equivalent surface treatment.
2) In Types 3 & 4 roads either:
a) Surface dressing or other surface treatment is not required when any binder course and surface course option permitted by section S6.4 is laid.
or b) The surfacing layers and equivalent surface dressing or other surface treatment shall be reinstated by agreement.
S6.4.7 Coated Chippings
1) All chippings shall be 14 mm or 20 mm nominal size, pre-coated in accordance with BS594: 1992
2) Where pre-coated chippings are to be embedded into a road surface, they shall be spread to give a chipping density reasonably matching that of the existing surface.
S6.4.8 Composite Roads
The total combined thickness of the reinstated binder course and surface course shall match the existing. Wherever practicable, the required surface course thickness should be maintained by adjustment of the binder course thickness.
S6.4.9 Single Course Construction
Where the existing road is of single course construction, permanent binder course material may be laid in place of a separate surface course, provided that the target binder content is increased by 0.5% above the BS4987 target value.
S6.4.10 Small Excavations and Narrow Trenches
1) A permanent surface course material in accordance with Appendix 2 may be laid in place of a permanent binder course material at base (roadbase) and/or binder course level.
2) Where this option is used there shall be no substitution of bitumen binder equivalence, as permitted under Appendix A11.
S6.5 Base and Edge Preparation
S6.5.1 Base Preparation
1) A tack coat shall be applied to the surface in the following circumstances.
a) Where bituminous material is to be laid onto an existing bituminous surface that has been trafficked or otherwise disturbed.
b) Where bituminous material is to be laid onto an existing bituminous surface laid more than 72 hours earlier.
2) The tack coat shall be applied at a rate of 0.3 to 0.5 litres per m 2, unless otherwise recommended by the manufacturer. The tack coat shall be applied evenly, with no pooling or dry areas.
3) A bitumen emulsion edge sealant may be used as a tack coat in small excavations and narrow trenches.
S6.5.2 Edge Preparation
S6.5.2.1 Edge Regularity
The edges of excavations may need to be trimmed, at binder course and/or surface course level, to meet the following requirements:
1) All bound edges shall be essentially straight, smooth and vertical.
2) All openings shall be "squared off", as necessary, to give a reasonably regular, plain shape when viewed from above, as shown in Figure S6.1
Figure S6.1 - Example of Prepared Edge
S6.5.2.2 Edge Sealing
1) At any interim stage and at the time of permanent reinstatement, the top 100 mm, at least, of all bound vertical edges at surface course and binder course levels, and the equivalent area on kerbs and exposed fixed features, shall be painted with a bitumen based edge sealant or otherwise prepared with an edge sealing system or equivalent material.
2) There shall be no significant splashing, spillage or any deliberate overpainting of the adjacent road surface, subject to the requirements of Section S6.5.2.5.
3) Tack coat material shall not be used as an edge sealant unless otherwise specified in S6.4.5.3
S6.5.2.3 Proximity to Road Edges, Ironwork, etc.
1) Where the "trimmed" edge of any excavation is within 250 mm of the road edge, kerbing, other fixed features or another reinstatement, the trim-line shall be extended to the interface with the road edge, kerbing etc.
2) The additional reinstatement area required by extending the trim-line may be confined to the surface course, provided the lower layers have not been damaged.
S6.5.2.4 Undercutting
All bound edges shall be essentially smooth and vertical with no significant undercutting, as shown in Figure S6.2.
Figure S6.2 - Example of Need for Trimback
S6.5.2.5 Overbanding
Overbanding or coating of the road surface at the interface between the existing road and the reinstatement edge is not mandatory, but may be beneficial when carried out in accordance with the following requirements:
1) The minimum skid resistance value (SRV) for all overbanding materials shall be 55 SRV.
2) Overbanding shall not exceed 3 mm thickness nor 40 mm width. Properly applied overbanding may be subject to spreading and may eventually wear away when subjected to trafficking. Overbanding which displays these characteristics shall not require intervention.
3) Overbanding shall not be used as a substitute for any edge sealing required in accordance with Section S6.5.2.2.
4) The SRV shall be measured in accordance with TRL Road Note 27, second edition 1969.
5) All materials used for overbanding shall have a current HAPAS Approval Certificate.
S6.6 Tolerances
1) All tolerances for all bituminous materials permitted in Appendix A2 in the reinstatement of flexible and composite roads, shall be in accordance with the requirements of Appendix A2.
2) Tolerances permitted for all other bituminous materials shall be by agreement.
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